• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.1
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• pp.51-56
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• 2013

This paper is the experimental study to investigate the noise sources location in order to reduce the noise level of line flow fan for the air conditioner in the subway car. The noise of line flow fan is caused by various factors such as the turbulence by air flow, random noise, noise of blade passing frequence(681Hz) and noise due to structural vibration of rotor unbalance(28.4Hz) by motor revolution. By performing the noise reduction on each sound source, the noise level is decreased as much as 5.7dB(A) through the controls of housing guide angle and distance, the configuration changes of flow passage shape and rotor balancing.

• Proceedings of the Korean Information Science Society Conference
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• 2010.06b
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• pp.173-178
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• 2010

최근 국내에서 홈네트워크에 관한 제품과 정책 및 제도의 개발이 다양하게 진행 중이고 대학에서의 관련분야 연구도 활발하지만 몇 가지 문제점이 있다. 첫째로 실험환경을 구축하는데 어려움이 있다. 홈네트워크 시스템에 사용되는 미들웨어나 게이트웨이 및 센서장비의 성능, 또는 지능형 서비스를 위한 알고리즘을 테스트하기 위해서는 실제 환경과 가까운 실험환경을 구축해야하는데, 비용과 시간의 측면에서 많은 부담이 있다. 둘째로 지능형 서비스를 위한 실험을 하기 위해서는 필수적으로 실 사용자가 실험환경에서 생활을 하여 실험을 하여야하는데 이 또한 많은 어려움이 있다. 그래서 본 논문에서는 이러한 문제점들을 해결하기 위해 상황인식 홈오토메이션 테스트베드를 구축하여 비교적 적은 비용으로 홈 네트워크 시스템을 테스트할 수 있는 방법을 제안한다. 2장에서는 홈게이트웨이에 대한 기본적인 배경지식에 대해 알아보고 본 연구에서 사용된 홈네트워크 미들웨어에 관해서 설명한다. 3장에서는 실험에 사용된 게이트웨이, 테스트베드, 통신방법에 대해서 설명한다. 5장에서는 실제로 홈오토메이션 시스템 테스트베드를 구현하고 5장에서 결론 및 향후연구에 관해 논한다.

• Journal of Power Electronics
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• v.15 no.4
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• pp.1119-1130
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• 2015

This study investigates the multi-objective fuzzy optimization of crowbar resistance for the doubly fed induction generator (DFIG) low-voltage ride-through (LVRT). By integrating the crowbar resistance of the crowbar circuit as a decision variable, a multi-objective model for crowbar resistance value optimization has been established to minimize rotor overcurrent and to simultaneously reduce the DFIG reactive power absorbed from the grid during the process of LVRT. A multi-objective genetic algorithm (MOGA) is applied to solve this optimization problem. In the proposed GA, the value of the crowbar resistance is represented by floating-point numbers in the GA population. The MOGA emphasizes the non-dominated solutions and simultaneously maintains diversity in the non-dominated solutions. A fuzzy-set-theory-based is employed to obtain the best solution. The proposed approach has been evaluated on a 3 MW DFIG LVRT. Simulation results show the effectiveness of the proposed approach for solving the crowbar resistance multi-objective optimization problem in the DFIG LVRT.

• Journal of Welding and Joining
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• v.30 no.4
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• pp.38-43
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• 2012

Using a fiber laser heat source, an oil pressure sensor was fabricated to measure the pressure in commercial vehicles. A stepping motor was used for the rotational and translational motion in the diaphragms and hardware joining. Laser welding process algorism including shielding gas control and vision system was integrated by using LabVIEW software for the high quality welding and in-line monitoring purpose. For the maximum flexibility in pressure transmission to the pressure sensor, thin sheet metal diaphragm, $25{\sim}50{\mu}m$(SUS-316L), was used and the diaphragms were optimally designed with FEM analysis. The welded samples were cross-sectioned the observation showed that the maximum depth ratio was more than seven times of diaphragms. The maximum welding speed was measured to be as high as 50in/mm by the developed automation mechanism. The fabricated prototypes were tested for the proof pressure, spring constant and sealing. The FEM results of spring constant measurement was as accurate as up to 80% of the design value and the sensor was safely operated up to the nominal pressure of 10bars.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.12
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• pp.177-184
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• 2001

C3M(chemical mechanical micro machining) is applied for diminishing the size of burr and fabricating the massless patterning for aluminium wafer(thickness of 1${\mu}m$). It is difficult to perform the micro size machining with the radically increased shear stress. While the miniaturization and function-orientation of parts has been needed in the many field such as electronics, optics and medicine. etc., it is not enough to satisfy the industry needs in the machining technology. In this paper feasibility test of diminishing burr and fabricating maskless pattern was experimented and analyzed. In the experiment oxide layer was farmed on the aluminium with chemical reaction by ${HNO_3}$(10wt%), then the surface was grooved with tungsten carbide tool for the different condition such as the load and fred rate. The result was compared with the conventional machining to show the improvement of C3M with SEM for burr diminish and XPS for atomic existence, AFM for more precise image.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.1
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• pp.82-88
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• 2001

The demands of high data transfer rate and high recording density in optical disk memory device are being increased. In this paper, 4 design parameters for next generation optical disk are investigated. As for the high data transfer rate, two design parameters such as driving acceleration and transmissibility are introduced. As the high recording density is concerned, the minimum linearity and the tilt of the actuator are introduced. Two kinds of pickup actuator are used to evaluate the validity of the parameters through the simulation and the experiment. The 4-wire actuator has good linearity but bad stability and tilt characteristics, while the rotary and axis actuator has good stability for the external vibration but bad linearity. It is demonstrated that the newly proposed design parameters are available to design and evaluate quantitatively the performance of the actuator for the next generation optical disk.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.1
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• pp.241-269
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• 2012

Wireless networks composed of multimedia-enabled resource-constrained sensor nodes have enriched a large set of monitoring sensing applications. In such communication scenario, however, new challenges in data transmission and energy-efficiency have arisen due to the stringent requirements of those sensor networks. Generally, congested nodes may deplete the energy of the active congested paths toward the sink and incur in undesired communication delay and packet dropping, while bit errors during transmission may negatively impact the end-to-end quality of the received data. Many approaches have been proposed to face congestion and provide reliable communications in wireless sensor networks, usually employing some transport protocol that address one or both of these issues. Nevertheless, due to the unique characteristics of multimedia-based wireless sensor networks, notably minimum bandwidth demand, bounded delay and reduced energy consumption requirement, communication protocols from traditional scalar wireless sensor networks are not suitable for multimedia sensor networks. In the last decade, such requirements have fostered research in adapting existing protocols or proposing new protocols from scratch. We survey the state of the art of transport protocols for wireless multimedia sensor networks, addressing the recent developments and proposed strategies for congestion control and loss recovery. Future research directions are also discussed, outlining the remaining challenges and promising investigation areas.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.11
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• pp.5110-5116
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• 2011

In this paper, multiplexing automation system will be proposed for the automobile electromotive mirror using CAN(Controller Area Network) protocol which has been known that it has a high reliability on the signal in the various network protocols. To do this, a master controller and two (input/output) slave controllers (H/W) are being made and application layer (S/W) is being programmed for effective going and communicating between subsystems. The possibility of the effectiveness of application and control ability will be shown when the system has minimum electrical lines by testing the experimental systems which was made up of the automobile electromotive mirror.

• Journal of Advanced Navigation Technology
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• v.17 no.6
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• pp.810-815
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• 2013

In case Wi-Fi network based First responder's position tracking system is used, range measurement must be generated from RSSI finger print database. However, it is impossible to build up finger print database and to perform rescue operation at same time in the scene of rescue. In this paper, improvised Wi-Fi network without finger print database and pedestrian dead reckoning based first responders tracking system is proposed.

• Journal of Surface Science and Engineering
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• v.40 no.4
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• pp.185-189
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• 2007

A scanning electron microscope (SEM) is a complex system, consisting of many sophisticated components. For a systematic characterization, a $2^4$ full factorial experiment was conducted. The SEM components examined include condenser lens 1 and 2 (denoted as A and B, respectively), and Objective lens (coarse and fine-denoted as C and D respectively). A statistical analysis was conduced to investigate factor effects and variations In response surfaces. Among four factors, main effect analysis revealed that A and D were Identified as the dominant factor. Moreover, B showed conflicting effect against C. The $R^2$ of statistical regression model constructed was about 69.6%. The model generated 3D response surface plots facilitated understanding of complex tactor effects.